Most people in the western world have way more computing power (and memory, and network bandwidth) than they would ever need. We as an industry have chosen to "borrow" that extra capacity through advertising and bitcoin mining and insanely wasteful webapps, but there's no reason we can't develop shared software, where the crawling, indexing etc all happens distributed - if StumbleUpon told me it will use 10% of my CPU to parse and index zero-knowledge encrypted data from other users, I would consider that a very good deal